1. Field of the Invention
The present invention relates to roofing of structures, and more particularly to a vinyl shingle roof covering product for installation on pitched roofs, and an improved method for roof covering installation.
2. Description of the Prior Art
Roofing is an ancient art. Through the ages roofers have used a variety of materials to shield roofed structures from the environment, including, but not limited to, thatch, asphalt, asbestos, slate, wood, and clay tile.
Conventional roofing materials suffer from a number of disadvantages. Asphalt and asbestos, for example, are both very heavy and brittle materials with a typical useful life of approximately 15 to 25 years. As these materials approach the end of their useful lives, they deteriorate in both appearance and function. Asbestos has been found to be an environmentally unsafe material, and is rarely used in roofing today. Clay and slate roofing material are also both heavy and brittle, and require a sturdy roof foundation to hold them in position. In addition, damaged clay or slate roofs are very difficult to repair. Finally, wood and thatch roofs suffer a serious disadvantage since neither is fire resistant. Certain shingles, such as asphalt shingles and wooden shakes, readily retain dirt and promote the formation of mildew under them.
The weight of roofing materials is important from several perspectives. First, the heavier the material, the higher the manufacturing and handling costs associated with production and shipping and distribution costs of the end product. Second, in order to accomplish their task, roofers must transfer roofing materials from the ground to the roof surface. Clearly, more effort, time, and expense is associated with transferring a heavy load than a light load. One of the most common roofing materials in use today is asphaltic shingle, which is provided in bundles. To install them, a roofer carries several bundles up a ladder and scatters them about the roof, then breaks each bundle open as needed. Asphalt is a very heavy material, and the granular wear surface on the shingle adds a considerable amount of weight.
The useful life of presently available asphalt shingle roofs is from 15 to 20 years. Roof guarantees are usually given for only 15 years.
Applicants are aware of the following U.S. Pat. Nos. concerning roofing materials and systems.
______________________________________ U.S. PAT. ISSUE NO. INVENTOR DATE TITLE ______________________________________ 3,605,369 Merrill Sept. 20, 1971 WOOD SIMULATING SHINGLE 3,619,343 Freeman Nov. 9, 1971 ROOFING MATERIAL 4,040,211 Wotherspoon Aug. 9, 1977 MULTI PORTION TILE HAVING A CURLED INTERLOCK 4,274,236 Kessler June 23, 1981 HIGH STIFFNESS CELLULAR PLASTIC SIDING 4,279,106 Gleason July 21, 1981 ROOFING PANEL 4,546,589 Seaman Oct. 15, 1989 SINGLE-PLY SEALED MEMBRANE ROOFING SYSTEM ______________________________________
The Seaman Patent teaches a single ply roof system for a flat roof, or "roof deck". The roofing is produced in rolls, applied from rolls, and held in place by nails along its edges. The edges of the sheets are heat bonded slightly overlapped, then they are heat bonded.
Merrill teaches a simulated shingle composed of a foam in a metal shell.
Kessler teaches a plastic siding also made of foam or PVC, which has reinforcing ribs on its underside.
Freeman teaches an expanded open-cell plastic roofing material, such as polyolefin foam, in which a single sheet covers the entire roof, but which requires an additional overlay material for sufficient protection from the elements.
Wotherspoon teaches simulated tiles with interlocking means which are quite complex, as best seen in his FIG. 4.
Gleason teaches a stiff roof panel in which the basic shell of hard plastic is filled with polyurethane foam.